Generally, an antibody is formed by forming a heterodimer by linking a heavy chain polypeptide having a high molecular weight with a light chain polypeptide having a low molecular weight by a disulfide bond, and forming a tetramer by linking two heterodimers again by a disulfide bond. The heavy chain-forming polypeptide consists of four domains, which include a variable domain, a constant domain 1, a constant domain 2 and a constant domain 3 from an N-terminus, and the light chain-forming polypeptide consists of two domains, which include a variable domain and a constant domain from an N-terminus. Among these, a conjugate of a variable domain of the heavy chain and a variable domain of the light chain binds to one antigen.
A reaction between an antigen, which is a chemical marker for labeling cells, and an antibody against the antigen indicates high specificity. An antigen site interacting with the antibody is called an antigen determinant or epitope, and the antigen determinant specifically binds to an antigen-binding site, which is a variable domain, of the antibody. Therefore, since the antigen-binding site may bind to only one antigen determinant, each of numerous antibodies may provide a unique immunity with respect to the antigen having a specific determinant.
Antibodies have a high stability in blood and a low antigenicity, and thus have attracted attention as a medicine. Among these antibodies, there is a bispecific antibody capable of recognizing two types of antigens. The bispecific antibody may be divided into two main types. The first-type bispecific antibody is modified by a recombinant DNA technique to have antigen-binding sites capable of binding to two different antigens, and in this case, one of the binding sites may be specific to any antigen, and the other one may be an antibody specific to another antigen and simultaneously binding to two antigens (Beck A et. al., Nat Rev immunology 10; 345-352, 2010). The second-type bispecific antibody is a very recently developed normal antibody, which has one antigen-binding site and a binding capability to two different antigens, and called a two-in-one antibody (Bostrom, J et. al., Science 323, 1610-1614, 2009). Since such a two-in-one antibody has one antigen-binding site, it can bind to one antigen at a time, rather than binding to two antigens, but has a capability of binding to two different antigens. The two-in-one antibody has a form of typical antibody that has been successfully developed, and thus is very favorable for development.
Since such a bispecific antibody may act by binding to a specific toxic cell and a target cell, it has a high target specificity.
As there is the growing understanding of the pathological physiology of rheumatoid arthritis, the concept of targeted therapy for regulating a disease by blocking the highly targeted material by anti-rheumatic drugs newly developed from the late 1990's came to the fore. As a result, as biological drugs formed by designing a material found as a target for a specific disease and capable of blocking the target are developed and used, they bring a great change in the treatment of rheumatoid arthritis. These drugs representatively include interleukin-6 antagonists (tocilizumab), CTLA4Ig (abatacept), and a B cell depleting agent (rituximab), as well as TNF-α inhibitors (etanercept, infliximab, adalimumab, etc.) and a recombinant interleukin-1 receptor antagonist such as anakinra, and are actually used clinically or in tests.
Studies on TNF-α (tumor necrosis factor-alpha) which targets tumors and sepsis in patients have already begun about 100 years ago. TNF-α is produced by macrophages, immune cells including B and T lymphocytes, non-immune cells, and various tumor cells, and plays important roles in a normal physiological inflammatory response and acquired and innate immunities. However, in an inflammatory disease such as rheumatoid arthritis, when TNF-α is inappropriately overproduced, various cells of an immune system are activated to induce a cytotoxic effect, and reactions such as inflammation, the destruction of tissues and organ damage appear. The main biological actions of the TNF-α are regulation of growth, differentiation, and metabolism in various types of cells; stimulation of lipolysis, inhibition of an activity of a lipoprotein lipase present in adipocytes, and induction of cachexia by stimulating hepatic lipogenesis; and induction of apoptosis. TNF-α is present in either a free form or a cell membrane-bound form. These two forms of TNF-α very strongly induce the inflammatory response of cells, and stimulate a disease state in a tissue. The cell membrane-bound TNF-α exhibits cytotoxic and inflammatory effects through cell-to-cell contact, and is detached from a cell membrane by a TNF-α convertase (TACE) and exists out of the cell. This TNF-α binds to one of the two receptors in blood, such as a TNF type I receptor (p55) or TNF type II receptor (p75), thereby exhibiting a biological activity. Clinically, overproduced TNF-α produces an inflammatory mediator stimulating macrophages in a rheumatoid arthritis patient and amplifying an inflammatory response, and expresses an attached molecule on a vascular endothelial cell to allow more inflammatory cells to be collected at an inflammatory site, and allows a fibroblast to produce a protease, resulting in damage to cartilages, bones and ligaments and thus exacerbating a disease.
Since, a TNF-α inhibitor was first approved by Food and Drug Administration (FDA) under the name of etanercept as a therapeutic agent for rheumatoid arthritis in November, 1998 and has been commercially available, infliximab and adalimumab have become commercially available, and new drugs improved in effects and side effects of the conventional drugs are being developed. Therapeutic reactions of the TNF-α inhibitor, the activity of a disease, structural damage corresponding thereto, the influence on the quality of life by a disease, and symptoms and signs generated by a disease vary depending on a patient. Also, sensitivity to a drug, a developing pattern of the effect or a side effect may also vary. Components, specific action mechanisms, pharmacological mechanisms and biopharmaceutical properties vary between various types of TNF-α inhibitors. For an animal test for demonstrating the efficacy of the TNF-α inhibitor, human TNF-α transgenic (Tg) mice were used, and in Tg197 mice, arthritis similar to rheumatoid arthritis occurs at the age of 4 to 5 weeks old, and from 9 to 10 weeks old, a remarkable limitation in the range of motion of the lower leg joint was observed.
CXCL10 (C-X-C motif chemokine 10), also known as interferon-gamma-inducible protein 10 (IP-10), is a 10 kDa chemokine induced by interferon gamma (IFN-γ). It is known that the CXCL10 has a chemotactic activity, and is involved in mitogenic activity. It is noted that the CXCL10 is secreted by various cells including endothelial cells, monocytes, fibroblasts and keratinocytes in response to IFN-γ, and present in epidermal macrophages and endothelial cells when delayed-type hypersensitivity (DTH) occurs on human skin. Also, the above-described reaction may be originally induced by IFN-γ, but also by IFN-α in dendritic cells and in central nervous system neurons due to stimuli such as IFN-γ, a virus and a lipopolysaccharide.
Receptors of CXCL10 are identified as seven transmembrane receptors, that is, CXCR3s. CXCR3s are expressed in activated T lymphocytes and monocytes, synoviocytes, endothelial cells, NK cells and eosinophils. It is known that two different ligands of CXCR3, that is, a monocyte/macrophage activating, IFN-γ-inducible protein (MIG) and an IFN-γ-inducible T cell alpha chemoattractant 1 (I-TAC), also bind to CXCR3. The binding of CXCL10 to CXCR3 mediates calcium mobilization and chemostasis in activated T cells and activated NK cells. In the thymus, CXCL10 is identified as a chemoattractant with respect to TCRαβ+CD8+ T cells, TCRγδ+ T cells and NK-type cells.
CXCL10 or its receptor CXCR3 is identified in a variety of different inflammatory and autoimmune diseases including multiple sclerosis, rheumatoid arthritis, ulcerative colitis, hepatitis, inflammatory myositis, spinal cord injury, systemic lupus erythematosus, graft rejection and Sjogren's syndrome. However, it has not been specifically known how such CXCL10 acts in an inflammatory response or immune response, except chemotaxis, in those diseases, and how important the CXCL10 is as a target for treatment.
In treatment of an autoimmune disease in which various inflammation mediators contribute to the causes of the disease, when several targets are neutralized with one type of antibody, other than a monoclonal antibody targeting a single antigen, the antibody may act as a more effective therapeutic agent. Attempts to recognize two targets with an antibody formed by combining two different antibodies have been already reported by several researchers. According to the recent study (Bostrom et al. Science 2009), an antibody simultaneously neutralizing vascular endothelial cell growth factors (VEGF) in an antibody library in which light chain CDRs of an antibody recognizing a human epidermal growth factor receptor 2 (HER2) are mutated was successfully screened. The antibody is a bispecific antibody recognizing both of mediators contributing to the causes of a disease, and particularly, has the same structure as normal IgG and a pharmacodynamic characteristic that can be expected, and is formed in both types of a bi- or monovalent antibody.
Throughout the specification, various publications and patents are referenced and citations are provided in parentheses. The disclosures of the cited publications and patents in their entities are hereby incorporated by references into the specification to fully describe the present invention and the state of the art to which the invention pertains.